Based on my understanding, when implementing the IRegionMemberLifetime
interface in a view (or view model) the KeepAlive property will be checked by the
RegionMemberLifetimeBehavior when the aforementioned view is deactivated in a region. If that property returns
false, the view is removed from the region automatically.

Hence, if your KeepAlive property of your views / view models are not being hit it could mean that the views (and view models) are not being deactivated from their corresponding region. For example, this could happen when using an
ItemsControl as a region, as this kind of region can contain more than one active view at the same time. Then, if you "navigate away" from your views in that type of region, the views would still be active and the
RegionMemberLifetimeBehavior will not try to check their
KeepAlive property.

It could be helpful if you could provide us with more information about your scenario and what you are trying to achieve so that we can help you further with this.